SparkFun INA2XX Arduino Library

SparkFun INA2XX Arduino Library

Arduino Library for the SparkFun Qwiic Power Monitor (INA228 / INA237)

The SparkFun Qwiic Power Monitor puts a Texas Instruments INA2XX-series digital power monitor on a Qwiic-enabled breakout, making high-side current, voltage, and power measurement as simple as plugging in a cable. The board carries a 15 mΩ shunt resistor and a screw terminal for the load and bus connections, so you can measure a supply rail without breaking out a meter.

This library provides an easy-to-use interface to both the INA228 (20-bit, high-precision, with energy and charge accumulation) and the INA237 (16-bit) over I2C, built on the SparkFun Toolkit. Both parts share the same register interface and the same library API — pick the class that matches your board and the rest of your sketch is identical. The library handles device setup and calibration for you and returns real-world readings in amps, volts, and watts, while still exposing the lower-level registers for advanced use.

Supported Devices

Device	ADC	Precision	Energy / Charge	Notes
INA228	20-bit	High (312.5 nV shunt LSB)	✅ 40-bit ENERGY + CHARGE accumulators	Use SfeINA228ArdI2C
INA237	16-bit	Standard (5 µV shunt LSB)	❌	Use SfeINA237ArdI2C

Functionality

The library exposes the full shared feature set of the INA228 and INA237:

• Current, bus voltage, shunt voltage, power, and die-temperature readings in engineering units
• One-call calibrate() for any shunt resistor and expected current range
• Selectable ADC range (±163.84 mV / ±40.96 mV) for a precision-vs-range trade-off
• Configurable ADC operating mode, conversion times, and sample averaging
• Energy (Joules) and charge (Coulombs) accumulation on the INA228
• A full alert/diagnostic system: over/under-voltage, over-current (via shunt), over-temperature, over-power, conversion-ready, and math-overflow flags
• Programmable alert thresholds (with millivolt convenience setters) and alert pin polarity/latch configuration
• Raw register accessors for every measurement when you need the unscaled value

‍[!NOTE] The INA228 and INA237 share an I2C register map but differ in register width and LSB scaling. The library captures those differences internally (the base driver is a template parameterized on the raw register types), so the same method calls work on both parts.

Hardware Connections

The board connects over I2C using the Qwiic connector — no soldering required. The INA2XX parts use a default 7-bit I2C address of 0x40, jumper-selectable across 0x40–0x4F.

Pin / Header	Use	Notes
Qwiic / I2C	Power + communication	Standard 3.3V Qwiic connection
VIN+ / VIN-	Current-sense path	Load current flows through the on-board 15 mΩ shunt between these terminals
VBUS	Bus voltage sense	Connect to the rail whose voltage you want to measure
ALERT	Alert / interrupt output	Optional — asserts on the alert conditions you enable

Using the Library

Installation

Install through the Arduino Library Manager by searching for SparkFun INA2XX, or download this repository as a ZIP and add it via Sketch > Include Library > Add .ZIP Library. This library depends on the SparkFun Toolkit, which the Library Manager will offer to install alongside it.

Getting Started

The I2C interface is provided by the SfeINA228ArdI2C and SfeINA237ArdI2C classes. Declare the object that matches your device:

 {c++}
#include <SparkFun_INA2XX.h>
 
// Uncomment the device you're using
SfeINA228ArdI2C myINA;
// SfeINA237ArdI2C myINA;

In setup(), start I2C and call begin(). begin() initializes the bus and confirms the device is present by checking its Device ID:

 {c++}
Wire.begin();
 
if (myINA.begin() == false)
{
    Serial.println("Power monitor not found, check your wiring!");
    while (1)
        delay(1000);
}

Calibration

Before reading current or power, calibrate the device for your shunt resistor and expected maximum current. The SparkFun board uses a 15 mΩ shunt; this example sets a 10 A maximum:

 {c++}
// calibrate(shuntResistanceOhms, maxCurrentAmps)
myINA.calibrate(0.015, 10.0);

calibrate() computes CURRENT_LSB and writes the hardware SHUNT_CAL register, after which all current, power, energy, and charge reads are automatically scaled. See Example 05 for using a custom shunt resistor and the reduced ADC range.

‍[!IMPORTANT] If you change the ADC range with setADCRange(), call it before calibrate() — the calibration math depends on the selected range.

Reading Measurements

Each measurement is returned through a reference argument:

 {c++}
float busVoltage = 0.0f, current = 0.0f, power = 0.0f, temperature = 0.0f;
 
myINA.getBusVoltage_V(busVoltage);   // Volts
myINA.getCurrent_A(current);         // Amps
myINA.getPower_W(power);             // Watts
myINA.getDieTemp_C(temperature);     // degrees C
myINA.getShuntVoltage_mV(busVoltage); // shunt drop in mV

If you only need the raw register value, getCurrentRaw(), getBusVoltageRaw(), getShuntVoltageRaw(), and getPowerRaw() return the unscaled readings.

A Note on Return Values and Error Handling

Most library methods return a SparkFun Toolkit error code (ksfTkErrOk on success, a negative value on failure) and pass the reading back through a reference parameter. This lets you tell a real reading of zero apart from a communication failure. For simple sketches you can ignore the return value:

 {c++}
float amps;
myINA.getCurrent_A(amps); // assume good data

For robust applications, check it:

 {c++}
float amps;
if (myINA.getCurrent_A(amps) != ksfTkErrOk)
{
    // Handle the communication error
}
else
{
    // amps holds a valid reading
}

Energy and Charge (INA228)

The INA228 adds 40-bit accumulators for energy and charge, read as doubles in Joules and Coulombs:

 {c++}
double joules = 0.0, coulombs = 0.0;
myINA.getEnergy_J(joules);
myINA.getCharge_C(coulombs);
 
myINA.resetAccumulators(); // clear the ENERGY and CHARGE registers

These methods exist only on SfeINA228ArdI2C.

Alerts and Diagnostics

The DIAG_ALRT register exposes the device's status flags and alert configuration. Thresholds can be set in raw counts or, for the common cases, directly in millivolts:

 {c++}
myINA.setBusOverVoltageThreshold_mV(14000.0f); // alert above 14 V
myINA.setAlertLatch(true);                      // latch the alert until read
 
bool overVoltage = false;
myINA.isBusOverVoltage(overVoltage);

See Example 02 and Example 06 for the full alert and diagnostic workflow.

Examples

The library ships with a set of examples that build from the basics to more advanced features:

• Example 01 - Basic Readings — current, voltage, power, and temperature
• Example 02 - Alert Configuration — thresholds, alert pin, and status flags
• Example 03 - Power and Energy — power plus INA228 energy/charge accumulation
• Example 04 - Advanced Config — ADC mode, conversion times, and averaging
• Example 05 - Custom Shunt Resistor — calibrating for your own shunt and ADC range
• Example 06 - Diagnostics — reading and interpreting the diagnostic flags

Documentation

API documentation is generated with Doxygen and published to GitHub Pages from the main branch.

Products That Use This Library

• SparkFun Qwiic Power Monitor (INA228 / INA237)

Contributing

If you would like to contribute to this library, please report issues and submit pull requests against the GitHub repository.

License Information

This product is open source!

This product is licensed using the MIT Open Source License

Please see LICENSE.md for more information.

• Your friends at SparkFun